1. Field
This disclosure relates generally to semiconductor processing, and more specifically, to a method for forming a dual metal gate structure.
2. Related Art
In the field of semiconductor processing, the use of polysilicon gate structures is becoming increasingly less feasible as gate dielectric thicknesses steadily decrease. As semiconductor processing moves away from the use of silicon dioxide as gate dielectrics in favor of dielectrics having a high dielectric constant (also referred to as high k dielectrics), polysilicon gates become more problematic. One solution to overcoming some of the problems introduced by polysilicon gates is to use metal gates. In dual metal gate processes, a first metal is used to form the gates for PMOS (p-channel metal oxide semiconductor) devices and second different metal is used to form NMOS (n-channel MOS) devices. Through the use of the different metals, the work functions can be optimized for each type of device. However, in conventional dual metal gate integrations, some processing steps, such as the metal etches and hard mask removals, can damage the high k gate dielectrics of the dual metal gate structures, thus degrading device performance.